Measurements of prompt photon production with the ATLAS detector

The production of prompt isolated photons at hadron colliders provides stringent tests of perturbative QCD and can be used to evaluate the probability density functions of partons in the proton. In this talk, we present the latest measurements of prompt photon production using proton-proton collision data collected by the ATLAS experiment at $\sqrt{s}=13$ TeV. This includes the differential cross-section measurements of isolated photon production as well as production of two isolated photons. We also present a measurement that probes the event topologies of prompt isolated photons produced in association with two hadronic jets. Each measurement is corrected for detector inefficiency and resolution and the results are compared to state-of-the-art theory predictions, indicating several interesting discrepancies. Studies on the modelling of various multi-photon processes in the state-of-art MC generators and fixed-order predictions will be presented.